The first Titan 23G prior to launch
|Function||Expendable launch system|
|Country of origin||United States|
|Height||31.4 meters (103 ft)|
|Diameter||3.05 meters (10.0 ft)|
|Mass||117,020 kilograms (257,980 lb)|
|Stages||Two or Three|
|Payload to LEO||3,600 kilograms (7,900 lb)|
|Payload to Polar LEO||2,177 kilograms (4,799 lb)|
|Payload to HCO||227 kilograms (500 lb)|
|Launch sites||Vandenberg SLC-4W|
|First flight||5 September 1988|
|Last flight||18 October 2003|
|Engines||LR-87 (one engine with two combustion chambers)|
|Thrust||1,900 kilonewtons (430,000 lbf)|
|Specific impulse||258 sec|
|Burn time||156 seconds|
|Thrust||445 kilonewtons (100,000 lbf)|
|Specific impulse||316 sec|
|Burn time||180 seconds|
|Third stage (Optional) – Star-37XFP-ISS|
|Thrust||38.03 kilonewtons (8,550 lbf)|
|Specific impulse||290 sec|
|Burn time||67 seconds|
|Third stage (Optional) – Star-37S|
|Specific impulse||287 sec|
The Titan 23G, Titan II(23)G, Titan 2(23)G or Titan II SLV was an American expendable launch system derived from the LGM-25C Titan II intercontinental ballistic missile. Retired Titan II missiles were converted by Martin Marietta, into which the Glenn L. Martin Company, which built the original Titan II, had merged. It was used to carry payloads for the United States Air Force, NASA and NOAA. Thirteen were launched from Space Launch Complex 4W at the Vandenberg Air Force Base between 1988 and 2003. 
Titan 23G rockets consisted of two stages burning liquid propellant. The first stage was powered by one Aerojet LR87 engine with two combustion chambers and nozzles, and the second stage was propelled by an LR91. On some flights, solid upper stages were flown, usually the Star-37XFP-ISS; however, the Star-37S was also used. 
A contract to refurbish fourteen Titan II missiles to the Titan 23G configuration was awarded to Martin Marietta in January 1986. The first launch occurred on 5 September 1988, carrying a classified payload for the US National Reconnaissance Office. Thirteen were launched, with the fourteenth going to the Evergreen Aviation Museum.  The final flight occurred on 17 October 2003, carrying a DMSP satellite. 
During refurbishment, the forward structure of the second stage was modified with the addition of a payload attachment fitting to attach the payload to the rocket, and installing a payload fairing to protect it during launch. The engines were refurbished, and the rockets' guidance and control systems were upgraded by Delco Electronics.
The former Titan IIIB pad at Vandenberg, SLC-4W, was modified to accommodate the Titan 23G, and was used for all thirteen launches.
|Date/Time (UTC)||Serial number||Third Stage||Payload||Outcome||Remarks|
|5 September 1988
|G-1||B-98/56||None||USA-32 ( Bernie)||Successful|
|6 September 1989
|G-2||B-75/99||None||USA-45 ( Bernie)||Successful||Spacecraft failed immediately after launch|
|25 April 1992
|G-3||B-102||None||USA-81 ( Bernie)||Successful|
|5 October 1993
|G-5||B-65||Star-37XFP-ISS||Landsat 6||Failure ||Star-37 failure, failed to achieve orbit |
|25 January 1994
|4 April 1997
|G-6||B-106||Star-37S-ISS||USA-131 ( DMSP-5D2 F-14)||Successful|
|13 May 1998
|G-12||B-84/80||Star-37XFP-ISS||NOAA-15 (NOAA-K)||Successful||Included oxygen tank from Titan II B-72|
|20 June 1999
|12 December 1999
|G-8||B-94/44||Star-37XFP-ISS||USA-147 ( DMSP-5D3 F-15)||Successful|
|21 September 2000
|24 June 2002
|G-14||B-71/72||Star-37XFP-ISS||NOAA-17 (NOAA-M)||Successful||Included oxygen tank from Titan II B-92|
|6 January 2003
|18 October 2003
|G-9||B-107||Star-37XFP-ISS||USA-172 ( DMSP-5D3 F-16)||Successful||Final Titan II launch|
A fourteenth rocket, G-10, based on Titan II B-108, but incorporating an oxygen tank from B-80, was not launched and is preserved at the Evergreen Aviation & Space Museum in McMinnville, Oregon. The remaining 42 Titan II missiles were stored at Davis-Monthan AFB with most being broken up for salvage. Four were transferred to museums.
Media related to Titan (rocket) at Wikimedia Commons
- Krebs, Gunter. "Titan-2". Gunter's Space Page. Retrieved 2009-04-29.
- Kyle, Ed (2009-04-14). "Titan 23G Data Sheet". Space Launch Report. Retrieved 2009-04-29.
- Wade, Mark. "Titan". Encyclopedia Astronautica. Retrieved 2009-04-29.
- Kyle, Ed. "Titan Launch History". Space Launch Report. p. 3. Retrieved 24 January 2014.
- Wade, Mark. "Landsat 6". Encyclopedia Astronautica. Retrieved 24 January 2014.